A dynamic 1H and 13C nuclear magnetic resonance study of cis-1,6-dimethyl-2,5,7,10-tetraoxabicyclo[4.4.0]decane (4a,8a-dimethylhexahydro-p-dioxino[2,3-b]-p-dioxin)

Abstract

The 1H and 13C n.m.r. spectra of cis-1,6-dimethyl-2,5,7,10-tetraoxabicyclo[4.4.0]decane have been studied over a wide temperature range (204–293 K). Temperature-dependent phenomena observed in both the 1H and 13C n.m.r. spectra can be attributed to a ring-inversion process between the enantiomeric forms of a double-chair conformation for the title compound. Line-shape analysis has been performed to obtain thermodynamic parameters for the ring-inversion process of these enantiomers. Molecular mechanics calculations have been used to obtain the minimum-energy conformation and to make structural comparisons with previous studies on 2,5,7,10-tetraoxabicyclo[4.4.0]decanes.